Diluter for laboratory titration

ABSTRACT

A diluter having a shaft, and a liquid holding body at one end of and coaxial with the shaft, of which the body has a ringshaped chamber of capillary width about its axis, and axially spaced ports providing sole communication between the chamber and the outside, and cam means in the body inclined to the body axis and exposed to the chamber for impelling liquid therein on oscillating the body about its axis.

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Gallant Sept. 11, 1973 [54] DILUTER FOR LABORATORY THTRA'HKON 3,276,84710/ 1966 Duff et al. 73/4254 P X Inventor: Reginald R. Ga a isto Co3,627,276 12/1971 Gllford 259/50 [73] Assignee: Linbro Chemical C0., IncNew FOREIGN PATENTS OR APPLICATIONS Haven, Conn' 1,448,191 11/1968Germany 73/4254 P [22] Filed: 1972 Primary ExaminerWilliam 1. Price [21]Appl. No.: 233,887 Assistant Examiner-Philip R. Coe

AttorneyWalter Spruegel [52] US. Cl. 73/425.4 P, 23/292,225599/l408l,[57] ABSTRACT 51 rm. Cl. G01n 1/10, BOlf 3/08 A dilute having a Shaft,and a "quid hdding [58] Field of Search 259/48, 49 50 51 one end of andcoaxial with the shaft, of which the body 259/53, 75, 76, 77 10];73/4254 p has a ring-shaped chamber of capillary width about its axis,and axially spaced ports providing sole communi- 5 References Citedcation between the chamber and the outside, and cam UNITED STATESPATENTS means in the body inclined to the body axis and exposed to thechamber for impelling liquid therein on gi g )2 oscillating the bodyabout its axis. 312521331 5/1966 Lancaster..........,......::.... 73/425.4 P 20 Claims, 5 Drawing Figures Patented Sept. 11, 1973 I 3,757,584

INVENTOR DllLUTER FOR LABORATORY TITRATION This invention relates tolaboratory titration equipment in general, and to dilutersfor laboratorytitration in particular.

Titration is performed by preparing dilutionsof graduated concentrationof the substance that is. to be analysed, and by determining the lowestconcentration in which the analysed substance just produces a productthat is clearly detectable, by discoloration or precipitation, forexample, upon reacting with a particular selected reagent. Moderntitration technique involves the use of a titration tray anda diluter,when the tray having rows of cup formationsofwhich those in at least onerow are dropwise supplied witha diluent, and the diluter, being in theform of a liquid holding cage at the end of a shaft or stem, is with itscage dipped into a solution to-be-analysed in order .to be charged toits full capacity withsuch solution by capillary action. The .diluter isthen dipped with its charged cage into the diluent in a first cupformation in .the tray, and is oscillated therein about the shaft axisin order completely to mix the solution charge with the diluent. Qn thenremoving the diluter from this cup formation in the tray, its cagewill'have been fullycharged with the mixture which is now a dilution ofthe solution to-be-analysed. The diluter is next dipped ,with itscharged cage into the diluent in the next succeeding cup formation inthe tray, and is therein oscillated to mix its charge with the diluent,as before. This procedure is repeated in each following cup formation inthe tray. An indicator is thereafter introduced dropwise into each ofthe involved cup formations, and by reference to the reactions whichoccur, such as discoloration or droplet formation, and .the order insuccession of thecup formation in which the reaction is firstdetectable, theconcentration of the selected substance in the initialsolution can be determined. With the volumes of the liquids involved intitration being exceedingly small, being in the order of a drop or twoof diluent in each cup formation in a tray,

' and being, in the case of the solution to-be-analysed,

equal to the capacity of the diluter cage which customarily is a smallfraction of a milliliter, it stands to reason that the results obtainedin titration will be inaccurate or even grossly false unless the dilutercage will, after each clip, not only hold exactly the same liquidvolume, but will also securely retain it during transfer to sueceedingcup formations in a tray, and will also mix its entire charge evenlywith the diluent in successive'cup formations. Therefore, in order thatthe diluter cage may function to meet the various requirements justmentioned, it is imperative that its capillary forces on the liquidsinvolved are comparatively powerful, yet its entire charge must, onoscillation of the diluter shaft, mix with the diluent in each cupformation not only freely but also evenly throughout.

It is among the objects of the present invention to provide a diluter ofthis type of which the liquid holding cage not only exerts relativelypowerful capillary forces on the liquids involved, but is also highlyeffective in freely and most evenly mixing these liquids throughout ineach cup formation in a tray, thereby fully to meet the aforementionedexacting requirements of diluters.

It is another object of the present invention to provide a diluter ofthis type which has a shaft and a cylindrical body at one ,end of andcoaxial with the shaft, of which the body forms the liquid holding cage,and is to this end provided with an internal ring chamber of capillarywidth throughout which is closed except for axially spaced ports forliquid passage to and from the chamber, with the chamberbeing alsoprovided with cam formations which act as impellers to pulsate liquidfrom the chamber alternately through the axially Spacedports onoscillating ithe diluter shaft about its axis. With this arrangement,the ring-shaped chamber may, even at minimum outer diameter of the bodyfor desirable good clearance from the customarily quite narrowperipheral :walls-of the cup formations in a tray, be easily kept at anentirely adequate volume and also effective capillary width, by spacingthe chamber .from the outer body periphery .by a relatively thin wall,and

the liquid in the chamber so near the outer body periphery will, onoscillation of the diluter during its dip into the diluent in a cupformation in a tray,be subjected to optimum centrifugal force whichassists the cam formations in operating the liquid holding cage as aneffective periodically-reversing pump for most thorough mixing of theliquids involved.

. .lt is a further object of the present invention to provide a diluterof this type in which the aforementioned ring chamber in the liquidholding body is further arranged so that on dipping the body intodiluent in a cup formation in a tray and oscillating the diluter shaftfor the aforementioned pumping performance of the body and ensuingmixing of the liquids, all the liquid in the cup formation at anyinstant, including that at the very bottom of the cup formation, iswithin effective pumping reach of the body, thereby to attain mostthorough andeven mixing of the liquids involved with a minimum number ofpumping pulses and, hence, operational oscillations of the body. This isachieved by forming the ring chamber in the body cylindrical over itsaxial extent, except near the dip end of the body where this chamberconverges inwardly toward the body axis and is open to a centralaperture in the bodys dip end-which is one of the aforementioned portsin the body, with this inwardly converging chamber part being, moreover,provided with a central post which extends axially therein and to theoutside of the bodys dip end through the central aperture therein withclearance therefrom all around, and this post terminating, outside thiscentral aperture but at fairly close spacing therefrom, in a narrow tipwith which the diluter is to bear against the bottom of .a cup formationin a tray. In thus bringing this tip to bear against the bottom of a cupformation, the same unfailingly keeps theport in the body's dip endspaced from the cup bottom at the built-in distance which is selected tobring all liquid in the cupvformation, including that at the very bottomof the-latter, within most effective pumping reach of the oscillatingbody. Moreover, the post with the terminating tip not only carries thering shape of the chamber in the body through theinwardly convergingchamber part at the body's dip end, but even forms theIport in thelatter into a ring-shaped port so that the same may take up asubstantial area portion of the body's dip end and thus be inparticularly close proximity to, and hence within quite effectivepumping reach of, liquid in the most restricted part of the liquid pathto and from the pumping body, i.e., the space between the bodys dip endand the part of the bottomof a cup formation confronting this dip end,yet the width of this ringshaped port maybe kept sufficiently smallsecurely to retain liquid therein, if only bys urface tension, when thebody is not oscillated for pumping action. Further,

with the bottoms of the cup formations in titration traps being mostlyV-shaped or round in section, the central tip on the diluter body, inbearing against such a bottom of a cup formation, will also accuratelycenter the body in the cup formation for most uniform mixing of theliquids in pumping action of the body. Also, with the tip on the diluterbody bearing against the bottom of a cup formation and thereby keepingthe bodys dip and spaced from the cup bottom as mentioned, this clip endcannot scratch the cup bottom in oscillation of the body for pumpingaction. Last, but not least, with a liquid charge in the ring chamberbeing completely enclosed and, hence, not exposed to the atmosphere,except at the narrow bottom port and at the few other and similarlynarrow ports in the body, the liquid charge will not be subject toevaporation which might conceiv ably lead to a wrong evaluation of asolution being analysed.

' Another object of the present invention is to provide a diluter ofthis type which is specially fitted for, and particularly effective indisplacing and thoroughly and evenly mixing liquids in, cup formationswith bottoms of a given section, by shaping the dip end of the diluterbody to conform to the section of the bottoms of such cup formations,and arranging the aforementioned tip on the body so that the dip end ofthe latter will be spaced from the bottom of a cup formation by auniform and quite narrow gap when the tip bears against the cup bottom.Thus, in lowering the diluter body all the way into a cup formation, itsdip end will displace all liquid it confronts until it reaches its finalposition in which it is spaced from the cup bottom by the mentioneduniform and quite narrow gap which affords no pocket whatever along thecup bottom in which liquid would not at all, or only poorly, mix withthe liquid remainder in operational pumping action of the body.

A further object of the present invention is to provide a diluter ofthis type in which the aforementioned liquid-impelling cam formations inthe ring chamber in the body are arranged not only to increase thevolume of the ring chamber, but also to increase the force of capillaryattraction of liquid into, and of its capillary retention in, the ringchamber without, however, impeding their liquid-impelling function inpumping action of the body. This is achieved by forming these camformations as grooves in the inner peripheral surface of the ringchamber, with these grooves being equiangularly spaced and equallyinclined to the body axis, and being also of identical width ofcapillary dimension. With this arrangement, the cam grooves will indeedincrease the volume of the ring chamber and also the force of capillaryattraction of liquid into, and of the capillary liquid retention in, thering chamber, as contemplated, yet these cam grooves will, onoscillation of the body for pumping action, exert on the confined liquidin the body axial displacement force components which are quiteeffective, since they easily overcome the capillary liquid retentivityof the body's interior as weakened as it then is by agitation of theconfined liquid due to operational oscillation of the body and alsocentrifugal force.

It is another object of the present invention to provide a diluter ofthis type of which the body has limited axial yieldability on the shaftwhich is adequate to take up such relative axial motion between shaftand body as may occur after the bodys tip has become seated on thebottom of a cup formation in a tray as, for example,

where titration is undertaken in apparatus in which a row of dilutersare with their shafts removably mounted on an overhead support and oneor more of their bodies are hardly perceptibly below the level of theremaining bodies, and the bodies are simultaneously projected intoaligned cup formations in a tray either by mechanically lowering thediluters or by mechanically raising the tray. To this end, the dilutershaft has an axial recess in one end, and the body has' a shank which isslidable in the shaft recess and has therein a lost-motion connectionwith the shaft, and a spring in the shaft recess urges the body stem tothat end of the lost-motion connection at which the body is at maximumprojection from the shaft.

Further objects and advantages will appear to those skilled in the artfrom the following, considered in conjunction with the accompanyingdrawings.

In the accompanying drawings, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

FIG. 1 is a view of a diluter embodying the invention;

FIG. 2 is a similar view, but partly in section, of the same diluter;

FIG. 3 is a cross-section through the diluter as taken on the line 33 ofFIG. 2; and

FIGS. 4 and 5 are fragmentary views, partly in section, of diluters ofdifferent modifications.

Referring to the drawings, and more particularly to FIGS. 1 to 3thereof, the reference numeral 10 designates a diluter having as itsmajor components a shaft 12 with an axis x, and a liquid holding body 14at one end of and coaxial with the shaft 12.

The body 14, which in this instance has an axial stem 16 for its mounton the shaft 12, is preferably formed in two parts 18 and 20, of whichpart 18 is a plug formation on the end of the stem 16, and part 20 is acap. The plug 18, which is joined to the stem 16 by a tapered top 22, isprovided with coaxial cylindrical formations 24 and 26, of which theformation 24 is next to the top 22, and the formation 26 projects fromthe formation 24 and has an end 28, with the cylindrical plug formation26 being of smaller diameter than the other cylindrical formation 24.

The cap 20, which is cup-like in shape, has an annular rim 30 and abottom wall 32 with a central, preferably circular, aperture 34. The cap20 is with the top end of its rim 30 fittedly received by thecylindrical plug formation 24 and is firmly secured thereto as by localstaking at 36, for example, with the cap 20 being, furthermore,accurately located axially on the plug 18 be resting with its rim top onan annular shoulder 38 on the plug. The rim 30 of the cap 20 surroundsthe peripheral surface 40 of the cylindrical plug formation 26 and isuniformly spaced therefrom by a capillary gap 42, while the cap bottom32 overlaps the end 28 of the cylindrical plug formation 26 and isunformly spaced therefrom by a capillary gap 44. The plug 18 andsurrounding cap 20 thus form a capillary chamber 46 which at 48 isring-shaped about the axis x over the axial extent of the peripheralwall 40 of the cylindrical plug formation 26, and at 50 convergesinwardly toward the axis x between the plug end 28 and the cap bottom32. The chamber 46 is closed to the outside except at axially spacedports, of which one is the aperture 34 in the cap bottom 32 and theremaining ports 52, in this instance four, are provided in the cap rim30 within the axial extent of the cylindrical plug formation 26. Theplug end 23 is also provided with an axial post extension 54 whichprojects through the port 34 in the cap bottom 32 to the outside thereofand there terminates in a preferably rounded bearing tip 56. The postextension 54 thus forms the post 34 in the cap bottom 32, and also theinwardly converging part 50 of the capillary chamber 46, ring-shapedabout the axis 1:. With the chamber 46 having capillary attraction toliquid within reach and holding liquid in this chamber by capillaryretention, the ports 34 and 52 are preferably of sufficiently restrictedarea to retain liquid at least by surface tension in order to avoid anyloss of liquid from the body 14 in certain phases of operation of thediluter involving transfer of the liquid-charged body from one cupformation to a next cup formation in a titration tray.

Operation of the diluter also involves mixing of a liquid charge in itsbody with liquid in a cup formation in a tray into which the body isdipped. To this end, the body 14 is provided with cam means inclined tothe axis x and exposed to the capillary chamber 46 for impellin g liquidtherein on oscillating the body about its axis. These cam means are inthe preferred form of grooves 60 of capillary width in the cylindricalplug formation 26 which preferably are equiangularly spaced, extend atthe same inclination to the axis x, and are coextensive over theirextent axially of the body 12. There are preferably four of these camgrooves 60 in keeping with the provision of the exemplary four ports 52in the cap rim 30.

For a reason explained hereinafter, the present diluter is alsospecially fitted for cup formations c with standard cone-shaped bottomsb in titration trays (FIG. 1). These cone-shaped bottoms b of cupformations c in a titration tray have a given angle A, and the capbottom 32 of the liquid holding body 14 of the diluter is formedfrusto-conical to conform to the cone-shaped bottom b of a cup formation0. Further, for proper dip of the diluter body 14 into liquid in a cupformation c, the tip end 56 of the post extension 54 on the cylindricalplug formation 26 is brought to bear against the cone-shaped bottom b ofthe cup formation, whereby the body 14 becomes also centered on the apexa of this bottom, with this tip end'56 being so spaced from thefrusto-conical cap bottom 32 thatthe latter will then be spaced from thecone-shaped bottom b of the cup formation by a uniform gap g which isquite narrow, being in the order of a few thousandths of an inch, butnevertheless sufficient to avoid scratching of the bottom b of the cupformation by the cap bottom 32 of the body 14 on operationallyoscillating the latter about its axis.

With the liquid holding diluter body 14 being required, for itsprescribed dip into liquid in a cup formation c in a tray, to bear withits tip 56 against the bottom b of the cup formation, contact betweenthem, either on lowering the diluter or raising the tray, is preferablycushioned to avoid possible damage to the diluter or tray. To this end,the stem 16 of the liquid holding body 14 has in its mount in the shaft12 a limited lost-motion connection with this shaft. Thus, the body stem16 is slidably received in an axial recess 62 in the shaft 12 (FIG. 2),and the lost-motion connection is in this instance provided by atransverse groove 64 in the stem 16 and a crosspin 66 in the shaft 12which extends through the groove 64, with the groove 64 having oppositewalls 68 and '70 of a given spacing, and the crosspin 66 being ofsmaller diameter than the spacing of the groove walls 68 and 70. Apreloaded spring 72 in the shaft recess 62 normally urges the body stem16 to one end of its lost-motion connection with the shaft 12 at whichthe groove wall 68 bears against the crosspin 66 and the body 14 is atits maximum projection from the shaft 12. Thus, hard and possiblydamaging contact be tween the tip 56 on the diluter body 14 and thebottom b of a cup formation c in a tray is avoided by the yield of thebody 14 relative to the shaft 12 which is afforded by the describedspring-loaded lost-motion connection.

In operation of the diluter for a given titration procedure, the body 14is first dipped into a solution to-beanalysed and its chamber 46 isthereby charged to its full capacity with solution by capillary action,with even the ports 34 and 52 being then charged with solution. Thechamber 46 is, by its restricted width, designed to exert on thesolution relatively strong capillary forces which not only assure quickcharging of this chamber to its full capacity with solution, but alsoexhibit relatively strong retentivity of the solution charge in thechamber 46 so that none of the charge will be lost in operationaltransfer of the diluter body'l4 into a cup formation in a tray. Havingonce been charged with solution to-be-analysed, the diluter is with itsbody dipped into diluent in a starting cup formation c in a tray (FIG. Iwith the cup formation being characteris tically small so that thediluent charge therein, usually one or two drops, more or less fills thebottom b of the cup formation prior to dipping the diluter body 14thereinto. On dipping the diluter body into the diluent in the cupformation 0, diluent will be displaced by the body 14 sufficiently toraise the level of the diluent to within reach of the body ports 52. Thediluter is then oscillated-at its shaft 12 about its axis x for pumpingaction of the body 14 and ensuing mixing of its charge with the diluentin the cup formation 0. In thus oscillating the body 12, various forces,such as hydrostatic pressure and centrifugal force, for example, towhich the charge in the capillary chamber 46 is subjected, has atendency to, and will, force at least some of the charge out of thischamber, but it is the cam grooves 60 in the body, with the assistanceof these forces, that impart to the body. 14 a pumping actionsufficiently powerful to overcome the capillary retentivity of thecharge in the chamber 46. Thus, these cam grooves 60 will, onoscillation of the body 14, exert on the confined charge in the latteraxial displacement force components which are quite effective, sincethey easily overcome the capillary liquid retentivity of the bodysinterior as weakened as it then is by agitation of the confined chargedue to operational oscillation of the body and also centrifugal force.The pumping action of the oscillating body 14 is, therefore, relativelypowerful, and is also periodicallyreversing, resulting in circulation ofthe liquids involved back and forth through the chamber 46 and ports 34and 52 and ensuing most thorough mixing of these liquids. Moreover, thepumping action of the oscillating body 14 results in mixing of theliquids involved not only most thoroughly, as described, but also quiteevenly throughout including at the very bottom b of the cup formation 0.Thus, in lowering the diluter body all the way into the cup formation 0,its dip end, i.e., the bottom 32 of the body cap 20, will displace allthe diluent it confronts until it reaches its final disposition on whichit is spaced from the bottom b of the cup formation by the uniform andquite narrow gap g which affords no pocket whatever along this cupbottom b in which liquid would not at all, or only poorly, mix with theremaining liquid in operational pumping action of the body.

With the bottom 32 of the body cap 20 being in this instancefrustoconical, the bottom end 28 of the plug 18 is preferably alsoformed frustoconical to keep the capillary width of the inwardlyconverging chamber part 50 uniform and preferably the same as that ofthe cylindrical chamber part 48. Also, while the cam grooves 60 in thecylindrical plug formation 26 extend over the greater part of the axialextent of the peripheral surface 40 thereof, these cam formationspreferably extend also into the frusto-conical plug end 28 as at 60'(FIG. 2) for optimum pumping action of the body 14 in operationaloscillation. Further, and also for most effective pumping action of theoscillating body 14, the ports 52 are located within the axial extent ofthe cam grooves 60 in the peripheral surface 40 of the cylindrical plugformation 26, and are preferably slightly below the upper ends of thesecam grooves.

The shaft, plug and cap parts 12, 18 and 20 of the diluter may be of anysuitable metal, and they are preferably of stainless steel. Further,among these parts, the shaft 12 and the plug 18 with its stem 16 arepreferably simple and inexpensive parts made and finished inscrewmachines, while the cap 20 is preferably a part which is drawn toshape and then simply punched or drilled for the provision of the ports34 and 52. The assembly of these parts is quite simple and inexpensive,merely requiring sliding of the cap part 20 over the plug part 18 andlocally staking the former to the latter, inserting the spring 72 andplug stem 16 into the axial recess 62 in the shaft part 12, and drivingthe crosspin 66 into the shaft 12.

The actual diluter is, of course, much smaller than shown. In thisconnection, there is given, by way of example only, an indication of theactual size of a diluter of highly satifactory performance in use withcup formations of accustomed size in a titration tray, with the outsidediameter of the cap part 20 of this diluter being about 0.170 inch, andits other dimensions being in about the same proportion thereto asappears in the drawings which show the diluter at a fairly true, butgreatly enlarged, scale.

Reference is now had to FIG. 4 which shows a modified diluter 10 that isin all respects like the described diluter 10 of FIGS. 1 to 3, exceptthat its liquid holding body 14' is specially fitted for cup formationsc with semi-spherical or so called round bottoms b in a tray. To thisend, the bottom 32' of the body cap 20' is formed part-spherical inconformity with the round bottom b of the cup formation, and the bearingtip 56' on the body plug 18', when seated on the bottom b' of the cupformation, holds the bottom end 32 of the diluter body 14' spaced fromthe round bottom of the cup formation by the uniform and quite narrowgap g.

FIG' shows another modified diluter which differs from the diluters l0and 10' by being specially fitted for cup formations c" with flatbottoms b" in a tray. To this end, the bottom 32" of the body cap 20 isformed flat, and the bearing tip 56" on the body plug 18", when seatedon the bottom b" of the cup formation, holds the bottom end 32" of thediluter body 14' spaced from the flat bottom of the cup formation by theuniform and quite narrow gap g".

What is claimed is:

1. A diluter, providing a shaft, a cylindrical body, having alongitudinal axis, at one end of and coaxial with said shaft, with saidbody having a ring-shaped chamber of capillary width about said bodyaxis, and axially spaced ports providing sole communication between saidchamber and the outside of said body, and cam means in said bodyinclined to said body axis and exposed to said chamber for impellingliquid therein on oscillation of said body about is axis.

2. A diluter as in claim 1, in which said chamber has spaced inner andouter peripheral surfaces, and said cam means are angularly spacedgrooves of capillary width in one of said peripheral chamber surfaces,with said grooves being inclined to said body axis.

3. A diluter as in claim 2, in which said grooves are in said innerperipheral chamber surface.

4. A diluter as in claim 1, in which said body has a free end remotefrom said shaft, and said chamber has main and end sections, of whichsaid main section is cylindrical about said body axis and has spacedinner and outer peripheral surfaces of given diameters, and said endsection is next to said body end and converges from said main sectioninwardly toward said body axis, with one of said ports being provided insaid body end and the remainder of said ports being within the axialextent of said main chamber section.

5. A diluter as in claim 4, in which said one port is centered on saidbody axis and its cross-sectional dimension is smaller than said givendiameter of said inner peripheral chamber surface.

6. A diluter as in claim 5, in which said body has in said end chambersection a coaxial post extending into said one port with clearancetherefrom throughout to thereby form said end chamber section and oneport ring-shaped about said body axis.

7. A diluter as in claim 6, in which said post extends through said oneport to the outside of said body and there terminates in a bearing tipaxially spaced from said body end.

8. A diluter as in claim 7, in which said bearing tip is rounded.

9. A diluter as in claim 7, in which said ports are of restrictedcross-sectional area for liquid retention by surface tension.

10. A diluter as in claim 7, in which said cam means are angularlyspaced grooves of capillary width in said inner peripheral surface ofsaid main chamber section, with said grooves being inclined to said bodyaxis.

11. A diluter as in claim 10, in which said grooves are equiangularlyspaced and extend at the same inclination to the body axis, and they arecoextensive axially of the body.

12. A diluter as in claim 11, in which said ports other than said oneport are within the axial extent of said grooves.

13. A diluter as in claim 7, in which said body end surrounding said oneport is frusto-conical.

14. A diluter as in claim 7, in which said body end surrounding said oneport is part-spherical.

15. A diluter as in claim 7, in which said body has a coaxial stem, andsaid shaft has in said one end an axial recess in which said stem isslidable but held against rotation relative to said shaft, and there isfurther provided an axial lost-motion connection between said stern andshaft, and a spring urging said stem to one end of said lost-motionconnection at which said body is at maximum spacing from said one shaftend.

16. A diluter as in claim 15, in which said shaft recess and body stemare cylindrical, said shaft recess has a bottom, and said lost motionconnection is formed by a transverse groove with spaced side walls insaid stem, and a crosspin in said shaft extending through said recessand groove and being of a diameter smaller than the spacing of saidgroove walls, with said spring being interposed between said stem andrecess bottom, and said crosspin cooperating with said groove in holdingsaid stem against rotation relative to said shaft.

17. A diluter providing a shaft with an axis; a plug at one end of saidshaft having upper and lower cylindrical formations coaxial with saidshaft and being of larger and smaller diameters, respectively, of whichsaid upper formation is next to said shaft and said lower formationprojects from said upper formation and terminates in an end; and acup-like cap having a cylindrical rim and a bottom with a centralaperture, of which said rim is fitted and secured to said uppercylindrical plug formation and surrounds said lower cylindrical plugformation at uniform capillary spacing therefrom, and said bottomoverlaps said end of said lower cylindrical plug formation and isuniformily spaced therefrom by a capillary gap, with said lowercylindrical plug formation and cap forming a capillary chamber, said caprim having within the axial extent of said lower cylindrical plugformation angularly spaced apertures which, together with said aperturein said cap bottom provide sole communication between said chamber andthe outside thereof, and said lower cylindrical plug formation having aperipheral surface with angularly spaced grooves therein of capillarywidth and inclined to said shaft axis for impelling liquid in saidchamber on oscillating said shaft about its axis.

.18. A diluter as in claim 17, in which said end of said lowercylindrical plug formation has an axially projecting post extending withclearance through said aperture in said cap bottom to the outsidethereof and there terminating in a bearing tip axially spaced from saidcap bottom.

19. A diluter as in claim 18, in which said cap bottom is frustoconical.

20. A diluter as in claim 18, in which said cap bottom ispart-spherical.

1. A diluter, providing a shaft, a cylindrical body, having alongitudinal axis, at one end of and coaxial with said shaft, with saidbody having a ring-shaped chamber of capillary width about said bodyaxis, and axially spaced ports providing sole communication between saidchamber and the outside of said body, and cam means in said bodyinclined to said body axis and exposed to said chamber for impellingliquid therein on oscillation of said body about is axis.
 2. A diluteras in claim 1, in which said chamber has spaced inner and outerperipheral surfaces, and said cam means are angularly spaced grooves ofcapillary width in one of said peripheral chamber surfaces, with saidgrooves being inclined to said body axis.
 3. A diluter as in claim 2, inwhich said grooves are in said inner peripheral chamber surface.
 4. Adiluter as in claim 1, in which said body has a free end remote fromsaid shaft, and said chamber has main and end sections, of which saidmain section is cylindrical about said body axis and has spaced innerand outer peripheral surfaces of given diameters, and said end sectionis next to said body end and converges from said main section inwardlytoward said body axis, with one of said ports being provided in saidbody end and the remainder of said ports being within the axial extentof said main chamber section.
 5. A diluter as in claim 4, in which saidone port is centered on said body axis and its cross-sectional dimensionis smaller than said given diameter of said inner peripheral chambersurface.
 6. A diluter as in claim 5, in which said body has in said endchamber section a coaxial Post extending into said one port withclearance therefrom throughout to thereby form said end chamber sectionand one port ring-shaped about said body axis.
 7. A diluter as in claim6, in which said post extends through said one port to the outside ofsaid body and there terminates in a bearing tip axially spaced from saidbody end.
 8. A diluter as in claim 7, in which said bearing tip isrounded.
 9. A diluter as in claim 7, in which said ports are ofrestricted cross-sectional area for liquid retention by surface tension.10. A diluter as in claim 7, in which said cam means are angularlyspaced grooves of capillary width in said inner peripheral surface ofsaid main chamber section, with said grooves being inclined to said bodyaxis.
 11. A diluter as in claim 10, in which said grooves areequiangularly spaced and extend at the same inclination to the bodyaxis, and they are coextensive axially of the body.
 12. A diluter as inclaim 11, in which said ports other than said one port are within theaxial extent of said grooves.
 13. A diluter as in claim 7, in which saidbody end surrounding said one port is frusto-conical.
 14. A diluter asin claim 7, in which said body end surrounding said one port ispart-spherical.
 15. A diluter as in claim 7, in which said body has acoaxial stem, and said shaft has in said one end an axial recess inwhich said stem is slidable but held against rotation relative to saidshaft, and there is further provided an axial lost-motion connectionbetween said stem and shaft, and a spring urging said stem to one end ofsaid lost-motion connection at which said body is at maximum spacingfrom said one shaft end.
 16. A diluter as in claim 15, in which saidshaft recess and body stem are cylindrical, said shaft recess has abottom, and said lost motion connection is formed by a transverse groovewith spaced side walls in said stem, and a crosspin in said shaftextending through said recess and groove and being of a diameter smallerthan the spacing of said groove walls, with said spring being interposedbetween said stem and recess bottom, and said crosspin cooperating withsaid groove in holding said stem against rotation relative to saidshaft.
 17. A diluter providing a shaft with an axis; a plug at one endof said shaft having upper and lower cylindrical formations coaxial withsaid shaft and being of larger and smaller diameters, respectively, ofwhich said upper formation is next to said shaft and said lowerformation projects from said upper formation and terminates in an end;and a cup-like cap having a cylindrical rim and a bottom with a centralaperture, of which said rim is fitted and secured to said uppercylindrical plug formation and surrounds said lower cylindrical plugformation at uniform capillary spacing therefrom, and said bottomoverlaps said end of said lower cylindrical plug formation and isuniformily spaced therefrom by a capillary gap, with said lowercylindrical plug formation and cap forming a capillary chamber, said caprim having within the axial extent of said lower cylindrical plugformation angularly spaced apertures which, together with said aperturein said cap bottom provide sole communication between said chamber andthe outside thereof, and said lower cylindrical plug formation having aperipheral surface with angularly spaced grooves therein of capillarywidth and inclined to said shaft axis for impelling liquid in saidchamber on oscillating said shaft about its axis.
 18. A diluter as inclaim 17, in which said end of said lower cylindrical plug formation hasan axially projecting post extending with clearance through saidaperture in said cap bottom to the outside thereof and there terminatingin a bearing tip axially spaced from said cap bottom.
 19. A diluter asin claim 18, in which said cap bottom is frustoconical.
 20. A diluter asin claim 18, in which said cap bottom is part-spherical.